DE7829334U1 - Prosthesis anchoring for hip joint prosthesis - Google Patents

Description

. ^: CARPENTER

PATENT LAWYERS

'' Dipl.-Ing. H. Leinweber <ΐΜο-7β)

Dipl.-Ing. Heinz Zimmermann Dipl.-Ing. A. Gf. v. Wengersky

Rosental 7 D-8000 Munich 2 2nd staircase (Kustermann-Passage) Telephone (089) 2603989 Telex 528191 lepatd Telegr. Addr. Leinpat Munich

^{d # n} October 2, 19/8

UnMr Zalditn

Wy / Sm

Dr. raed Adolf Voorhoeve, 6250 Limburg / Lahn 1 Prosthesis anchoring for hip joint prosthesis

When inserting hip joint prostheses with artificial cements, mechanically inadequate anchoring of the prosthesis shaft has so far often resulted for various reasons. Over time, these more or less quickly lead to loosening of the prosthesis or to prosthesis breakage. The currently available implants and materials (bone cements) cannot always prevent such complications. Particular difficulties arise when ^ν · = ϊ repeat surgery due to loss of bone substance on the inside (medial side) of the thigh and a mechanically secure anchoring of the prosthesis is not possible because the prosthesis is not supported. Numerous clinical cases and their static calculation show that the currently available bone cements as well as the numerous variations in the shape of the prosthetic stems used. six who can cope with the problem outlined above.

sought, failures could not be avoided. One static Secure anchoring does not come about when the prosthesis is seated on the medial side of the thigh Bone defects have arisen. Until now, such bone defects could only be covered with bone cement.

be bridged. The relatively brittle bone cement is the

! Significant pressure, bending and and shear forces in the long run and is shattered. There is then an alternating bending stress on the prosthesis

; metal shaft. This either leads to loosening of the prosthesis shaft or to anchoring by the maximum tensile forces on the opposite side and as a result, the prosthesis shaft breaks.

The task of the innovation is to improve the mechanical strength to improve the anchoring of the prosthesis.

This object is achieved according to the invention by a between the prosthesis shaft and the bone wall of the prosthesis shaft funnel mesh that can be inserted into the receiving bone cavity. This is expediently made of steel, preferably stainless steel. If now the prosthesis shaft is not directly in the with Bone cement-filled bone cavity inserted, but into the funnel network filled with bone cement and with these: into the bone cavity, this creates a steel mesh and bone cement construction that encompasses the prosthesis shaft. This cares for mechanically one / and-free conditions by converting the previously harmful bending and shear forces on the medial side into tensile forces be converted on the outside and in particular the previously possible point loading with high Load peaks is converted into a surface load with a far lower Belasuntsspitze. Using the funnel

S.

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netzes prevents the shattering of the bone cement on the medial side and the cracking of the prosthesis socket from the opposite side. The use of the funnel network also counteracts the loosening of the Iuiplantates. In this way, prosthesis anchors with significantly improved mechanical strength are created.

The funnel network can be produced in the most varied of ways. So it can cross each other out and with each other connected threads exist. Such a shape of the funnel network allows deformation of the network during insertion not only in a direction perpendicular to the mesh surface, but to a certain extent also in the surface. Yet the prefabricated funnel net results in good forest stability and, moreover, a good ability to convert point loads into surface loads. Instead of this The funnel net can also consist of sheet material pierced by numerous openings. A funnel network under certain circumstances, this construction is even easier to manufacture and is capable of forces not only along threads, but rather to transmit and distribute them within the material surface along all the lines of force that arise.

The conditions for use in the context of hip joint replacement accordingly, the funnel opening of the funnel network preferably has an elliptical cross section, while the cross-section merges into a circular shape in the direction of the funnel tip and gradually diminishes or has a constantly reduced diameter.

The needs when inserting the prosthesis socket

a ·· ··· ψ mi

Corresponding to the bone cavity, the funnel network, seen from the side (ventral side), has an approximately alphorn-like outline with gradually increasing curvature of the funnel network symmetry axis starting from the funnel tip, whereby the funnel opening lies in a plane on which the funnel network axis of symmetry is perpendicular or forms an angle of at least 60 ° with this. This shape is therefore the shape of the Bone cavity or the shape of the prosthesis shaft approximately adapted and thus results when it is stored in the bone cement a particularly good distribution of forces.

The funnel tip of the funnel net can be adjusted as required be hemispherical closed or simply open. The open version is easier to manufacture.

Under certain circumstances it is advisable to make the funnel network double-walled or the prosthesis anchoring from two to manufacture nested funnel nets with aligned openings. The internal funnel network serves as a the actual prosthetic mesh, while the external special mesh provides the mechanical strength achieved by the prosthetic mesh still improved. If the double-walled funnel network consists of two one inside the other with an aligned funnel opening simple funnel networks, these expediently show a difference in length of more than 10 ^. The double-walled Funnel network is used when static calculations show that the simple funnel network is not sufficient.

In addition, the wall thickness of the funnel net can be lengthways the funnel net length and / or along the funnel net circumference change. It is particularly useful in the case of the double-walled

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Funnel net construction the outer funnel net in the area the funnel opening have an enlarged wall thickness. This increased wall thickness should at least on the medial side present where a minor or major bone defect is present. For all cases in which there are large "medial bone defects or the bone as a result of numerous previous operations is hollowed out and an anchoring of a conventional prosthesis is not possible, double-walled ones are Funnel net construction and in particular the double-walled -. Funnel net construction with reinforcement on the medial side V / and strength of the special network - it is ideally suited.

In summary, the following can be said about improving the anchoring of the prosthesis: So far, interventions in which a hip joint endoprosthesis was used, no ideal mechanical prerequisites for permanent prosthesis anchoring. Rather, there was a risk of premature loosening or fracture of the prosthesis from the outset. the numerous factors that cannot be calculated in individual cases (weight of the patient, prosthesis fit, length of the femoral neck, Diameter of the thigh bone, condition i.e. stability of the bone) do not allow an exact calculation of the achieved stability of the prosthesis anchorage. Now but can be an exact calculation of the required reinforcement of the prosthesis anchorage through the funnel network in carry out each case before the operation and calculate an individual statics adapted to the patient Operation can be considered. The funnel network is thereby in different, the average values of the bone diameter adapted diameters and body weight and wall thicknesses adapted to other criteria are available represents. The use of the single or double-walled | Funnel nets are particularly recommended in the following cases: »

! Corrective interventions make the hip joint endoprosthesis bad ; with a wide medullary cavity in which the prosthesis shaft rotates ■ or. in the case of bone defects on the seat of the prosthesis; Leg-

Neck fractures, namely lateral fractures in which a -ideal seating of the prosthesis cannot be achieved or medial fractures with defects on the seat; Eotation : Instability of the prosthesis due to the medullary cavity being too wide; Osteopcrosis with greatly reduced load-bearing capacity of the decalcified bone; ■ all uncertain cases in which an all-round conclusive The prosthesis does not sit on; Cases of large defect range on the media side.

! In the drawing, the innovation is illustrated, for example. With regard to the disclosure of all ^r th details unspecified erläute below explicit reference is made to the drawings. Show it

Fig. La a section through a hip joint-> endoprosthesis,

¹ Fig. Ib and Ic a ventral view and a medial view of the standard shape of the funnel network used in Fig. La,

Fig. Id, Fig. Ie and Fig. 1f sections in the "Jinien A-A, B-B or C-C from Fig. La,

FIGS. 2a to 2f show views of a long form of the funnel network corresponding to FIGS. 1a to If,

FIGS. 3a to 3e correspond to FIGS. 1a to 1e

Views, a universal form of the funnel network,

FIGS. 4a "to 4f correspond to FIGS. 1a to If Views of a double-walled funnel network, and

5 shows a view of an insertable space-keeping instrument used in the double-walled funnel net.

Fig. Ta shows a hip joint prosthesis 10, the prosthesis shaft 11 engages in the bone cavity 12 of a bone 13 and must be anchored in this. The one remaining between the prosthesis shaft Π and the bone wall 14 of the Küoohenhöhle 12 Free barely is filled with 15 bone cement. In this way, the hip joint prosthesis 10 is anchored in the bone cavity 12.

To improve the anchoring of the prosthesis, a funnel mesh 16 is now inserted into the bone cement 15. The funnel network 16 is made of stainless steel. Its network structure is achieved by manufacturing it from steel wires or threads or by using a steel foil of sufficient thickness provided with appropriate openings. The funnel network 16 is shown in Fig. Ib in its Fig. La corresponding * ventral view and in Fig. 1c in its medial view. The hip joint prosthesis 10 is indicated by dashed lines in FIG. 1b, while only the prosthesis shaft 11 is shown in FIG. It is seen that the funnel-web 16 is approximately bent similar to the prosthesis stem 11 _t the inner wall vebei the funnel network, the outer wall of the Protheaenschaftes Π in the hemispherical closed funnel tip more approaches, which also applies to the area of the funnel opening, while on in a funnel opening near Zrfischenbereich the medial side a considerable distance between prosthesis shaft 11 and

M ι ι ι t

Funnel network 16 exists, while on the opposite side a greater distance closer to the funnel opening to Available. In the area of the funnel opening, the funnel network is in practically direct contact with the hip joint prosthesis TO.

The cross-sectional views allow the. ..ge of the prosthesis stem 11 in the funnel network 16 can be seen even more precisely. In particular, it can be seen in Fig. 1d that the funnel network in the area the funnel opening has a multiplied wall thickness on the medial side. In this way, the most frequently exposed area for holding the prosthesis can be found in this bone defect mechanical strength values can be achieved which are able to stabilize even larger amounts of bone cement. Overall, the funnel network 16 inserted into the bone cement 15 results in a good load distribution in the prosthesis anchoring and thus a considerably improved durability.

2a to 2f show a long funnel network shape, as is significant for hip joint prostheses 10 compared to FIG extended prosthesis shaft 11 can be used. Here, too, as can be seen from the figure, the dimensioning of the funnel network 16 chosen so that between the funnel network 16 and Prcthesensehaft 11 there is still enough space for Bone cement 15 remains. The one in the Ventralansijht | of Fig. 2b recognizable alphorna ^ term outline by extending the portion of the funnel network 16 with a reduced diameter emphasized even more.

3a to 3e show a funnel network 17 in universal form with open funnel tip 18. Through the open funnel

18 it is possible to use the universal shape in the form of the funnel network 17 regardless of the length of the Prosthesis shaft 11 of the hip joint prosthesis 10 to be used. If the prosthesis shaft 11 is longer than the funnel net 17, in this way, the prosthesis shaft 11 can protrude more deeply into the bone cavity 12 through the open funnel tip 18. Yet is capable of the funnel network embedded in the bone cement 15 17 ensure that the surface loads are evenly distributed. In the figure, there is also a small dashed line α medial bone defect 19 indicated by the corresponding on the medial side, increased wall thickness of the funnel network 17 in the area of the funnel opening, likewise mechanically secured because this reduces the compressive forces concentrated in the area of the bone de-effect Ί9 and also affects the entire prosthesis anchoring can be distributed. details the universal shape of the funnel network 17 can also be seen in FIGS. 3b to 3e.

Fig. 4a shows a bone 13 with dashed lines large medial bone defect 20. A double-walled special shape of the funnel mesh is provided for this. These is also used when the bone 13 has already had a very large bone cavity due to numerous previous operations. 12 has.

The double-walled funnel network consists of an internal one that directly encompasses the prosthesis shaft 11 Prosthetic network 21. The standard and universal funnel network shapes of the funnel networks explained above are used as the prosthesis network 21 16 and 17 suitable. A reinforcement of the wall thickness on the medial side is not necessary for the prosthesis network 21. A special network 22 is used as the external network

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can correspond to the Langforra explained above with reference to FIG. 2 and an enlarged one in the area of the large bone defect 20 Should have wall thickness. The special network 22 differs from the long form of the funnel network explained above especially due to its larger diameter in the area of the funnel opening.

The prosthesis network 21 is made up of an inner layer of cement 23, the special network 22 by an outwardly adjoining one Cement layer 24 anchored. In the figure, the shaft of a possible long prosthesis is also dashed indicated. If this is used, the Prοthesennetζ 21 with an open funnel opening was used to obtain the double-walled funnel net construction.

When setting up the funnel nets 16, 17 proceed as follows:

First, the bone cavity 12 of the thigh bone 13 is drilled out step by step. It then becomes a network of funnels selected whose diameter is 2 to 3 mm smaller than the diameter of the counter bore. For example, if the The diameter of the borehole is 17 mm, creating a funnel network tsit was selected with a diameter of the funnel tip of 14 mm. The irichternetz 16, 17 is then filled with bone cement 15 is pressed into the bone cavity by the hip joint prosthesis 10 or the prosthesis shaft 11 engaging in the funnel network and anchored in this by hardening of the bone cement 15.

With the double-walled 'frichternetz' a special one must be Surgical techniques were used. First of all, there is preparation of the bone 13 as described above. It will ever

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but then the special net 22 is selected according to the specified conditions and hammered into the bone cavity 12 with a special hammering device with bone cement. To create space during curing of the cement for the synthesis network with the professional 21 to be inserted acetabular prosthesis 10 so-% is then introduced into the remaining after breaking inner opening of the I special network 22 is a Platzhalteinstruraent 25 and I to 3UR curing of the outer layer of cement 24 in place Leave place.

Fig. 5 shows the space-retaining instrument 25 in its I position during the hardening of the cement layer on the outside

I 24. The part of the space holding device that is to be sunk into the thigh

I instrument 25 corresponds ii shape of Prothesenj that shank 11 of the hip joint prosthesis to be used with a 10 X supplement of 2 to 3 mm in diameter and from 2 to 3 cm in the length I. This addition creates sufficient space for the prosthesis network 21 and the cement layer 23 S on the inside. In the space created by the retaining tool 25 ί bed, the hip joint prosthesis 10 with the prosthesis I nefcs then is cemented 21st In special cases it is also conceivable to introduce the double-walled funnel network directly with the hip joint prosthesis 10 into the bone cavity 12. It is expedient to ensure that a sufficient amount of bone cement is present in the bone cavity as well as in the funnel net.

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Claims (1)

6. Prosthetic anchorage according to one of claims 1 to b, characterized in that the funnel network (16, 17, 21, 22) a circular cross-section at a distance from the funnel opening with diminishing in the seal to the funnel tip (1ö) Has circle diameter. 7. prosthesis anchorage according to claim 5 and 6, characterized - 13 - - 12 protection claims: 1. Prosthetic anchorage for hip joint prosthesis, marked through a between the prosthesis shaft (11) and the bone wall (14) of the bone cavity receiving the prosthesis shaft (12) insertable funnel net (16, 17, 21, 22), the starting from the funnel opening to the funnel tip (18) tapers and the funnel wall of numerous openings] is broken. 2. .Prothesis anchoring according to claim 1, characterized in that the funnel network (16, 17 ₅ 21, 22) consists of steel. ?, Prosthesis anchoring according to claim 1 or 2, characterized characterized in that the funnel network consists of intersecting and miteina? * the connected threads. 4. prosthesis anchorage according to claim 1 or 2, characterized in that the funnel network consists of sheet material. 5. Prosthetic anchorage according to one of claims 1 to 4, characterized in that the power network (16, 17, 21, 22) has an elliptical cross-section at the funnel opening. ! - 13 - characterized in that, seen in the direction of the main axis of the ellipse, a short section diminishes at the funnel opening! Cross-sectional width adjoins which is at least twice as long a section of constant cross-sectional width in the direction of the funnel tip (17) .. 8. Prosthetic anchorage according to one of claims 5 to 7, characterized in that, viewed in the direction of the minor axis of the ellipse, the funnel network (16, 17, 21, 22) is like an alphorn Has outline with gradually increasing curvature of the funnel network axis of symmetry starting from the funnel tip (18) and the funnel opening lies in an Eoens on which the funnel network symmetry axis is perpendicular or with this forms an angle of at least 60 °. 9. Prosthetic anchorage according to one of claims 1 to 8, characterized in that the funnel network is closed hemispherically at the funnel tip. 10. Prosthesis anchorage according to one of claims 1 to 8, characterized in that the funnel network is open at the funnel tip (18). 11. Prosthetic anchorage according to one of claims 1 to 10, characterized in that the funnel network is double-walled is formed (Fig. 4). 12. Prosthesis anchoring according to claim 11, characterized in that that the double-walled funnel network of two with aligned funnel opening into each other / ordered simple Consists of funnel networks (21, 22), - 14 - 13. Prosthesis anchorage according to claim 12, characterized in that ge · - f indicates that the two simple funnel networks (21, 22) | have a difference in length exceeding 10? 6. 14. Prosthetic anchorage according to one of claims 1 characterized to 131 characterized in that the _{Trichternetzwand-!;} strength changes along the length of the funnel net and / or along the S funnel net length. 15 »Prosthesis anchoring according to claims 13 and 14, thereby characterized in that the outer Triehfernetz (22) in the area | the funnel opening has an increased wall thickness. J